java.sql.SQLException: Illegal operation on empty result set. when authenticating

Question

What I\'m trying to do is:

1. Accept username(uname) and password(passw) as an input from the user.

2. Using ResultSet, retrieve the

Answer 1

@Eran mentioned the error by which a wrong id would yield an empty result set on which fields were gotten.

I still have small remarks:

• Try-with-resources take care of closing even in case of an exception or returning.
• For a local database you can send the password to SQL.
• Best to store passwords encrypted, when ever your database should get stolen.

Thus:

boolean loggedIn = false;
try (PreparedStatement stmt =
        conn.prepareStatement("SELECT 1 FROM admin WHERE id = ? AND pass = PASSWORD(?)")) {
    stmt.setString(1, uname);
    stmt.setString(2, passw);
    try (ResultSet rs = stmt.executeQuery()) {
         loggedIn = rs.next();
    } // Closes rs.
} // Closes stmt.

Answer 2

You are supposed to use the result of rs.next() :

            if (rs.next()) {
                n=rs.getString("id");
                m=rs.getString("pass");
            }

If rs.next() returns false, this means the query returned no rows.